In a conventional weft knitting machine, various modified knitting organizations are produced by combining three basic positions of knitting, tucking and welting (missing) in knitting operations by means of knitting needles. In a structure of a typical weft knitting machine, a carriage reciprocates along a needle bed having a plurality of needle grooves in a longitudinal direction, and each knitting needle performs knitting operation through a cam mechanism included in the carriage. The carriage is accompanied with a yarn supply member for supplying a knitting yarn to the knitting needles which perform knitting operation, and the plural knitting needles sequentially carry out the knitting operation in correspondence with the yarn supply position of the yarn supply member. The cam mechanism is basically formed to correspond to the knitting operation in the knitting position, and a needle selecting apparatus for selecting the knitting needles for the tucking or welting position is provided in each needle groove.
The applicant of the invention previously proposed needle selecting apparatus in Japanese Unexamined Patent Publications JP-A 6-200454, JP-A 6-220752, JP-A 9-241952 and other publications. FIG. 13 schematically shows a structure of a needle selecting mechanism disclosed in JP-A 9-241952, which is partially modified for the sake of descriptive convenience. A weft knitting machine 1 has a carriage 3 which reciprocates along a needle bed 2 extending in a longitudinal direction. Grooves to which needle plates 4 are fitted in predetermined intervals are formed on the needle bed 2 in the longitudinal direction. Needle grooves 5 are provided between the needle plates 4, and knitting needles 6 are disposed in the needle grooves 5 where the knitting needles 6 can be slidingly displaced. The weft knitting machine 1 includes at least a pair of the front and rear needle beds 2 whose front faces extend in parallel with the longitudinal direction, and the needle beds 2 are opposed to each other with a needle bed gap 7 interposed therebetween. However, only a side cross section of one of the needle beds 2 is shown in this figure and the other is omitted for the sake of descriptive convenience. Also, the sliding displacement direction of the knitting needle 6 is inclined upward toward the needle bed gap 7, but the inclination of the needle bed 2 is omitted and such a posture that the knitting needle 6 is slidingly displaced in a horizontal direction is shown. The carriage 3 is attached to the front and rear needle beds 2 in such a manner as to cross over the needle bed gap 7, and is accompanied with a yarn supply member for supplying a knitting yarn along the needle bed gap 7.
The knitting needle 6 has a needle main body 8 as the front haft and a needle jack 9 as the rear half when the needle bed gap 7 is the front and the opposite side is the rear in each needle groove 5 as viewed from the side of the weft knitting machine 1. A hook and other components for receiving a knitting yarn used for knitting operation are provided at the front end of the needle main body 8. The needle jack 9 has a driving butt 9a for advancing and retracting the knitting needle 6 within the needle groove 5. The needle jack 9 disposed in the needle groove 5 has a bent shape such that the butt 9a can project toward the carriage 3 by elasticity. When the butt 9a projects toward the carriage 3, a knitting cam 10 provided on the carriage 3 acts on the knitting needle 6, whereby the needle 6 can advance and retract in the needle groove 5 with respect to the needle bed gap 7.
A needle selecting apparatus 11 is provided for each knitting needle 6 for controlling the action of the knitting cam 10 given to the knitting needle 6. The needle selecting apparatus 11 includes a selecting jack 12 and a selector 13. The selecting jack 12 is disposed in the rear region of the needle jack 9 near the carriage 3, and a butt 12a projects toward the carriage 3. The position of the selecting jack 12 is determined by the selector 13 such that the butt 12a is positioned in any of B position, H position and A position. The selector 13 has butts 13a, 13b and 13c which project toward the carriage 3, and is shifted within the needle groove 5 by the action of a selector cam 14 provided on the carriage 3. When the selector 13 shifts to the front, a tip 13d pushes and advances the selecting jack 12. The advanced position of the selecting jack 12 is determined by action of a needle selection actuator 15 which is disposed near the carriage 3 in such a position that the rear half of the selector 13 is sandwiched between the needle selection actuator 15 and the selector cam 14.
The selector 13 disposed in the needle groove 5 has a bent shape such that an armature 13e formed in a position facing the needle selection actuator 15 in the rear half region can be separated from the needle selection actuator 15 by elasticity. When the selector cam 14 pushes the butt 13c disposed in the rear region, the armature 13e contacts the needle selection actuator 15 and is magnetically attracted thereto. The needle selection actuator 15 has two release positions, for example, where the attraction is released to conduct needle selection by energization for each knitting needle 6. The selector cam 14 has cam grooves in positions corresponding to the respective release positions so as to advance the selector 13 when the attraction for the armature 13e of the selector 13 is released and the butt 13b projects toward the carriage 3. When the attraction for the armature 13e is released in the release position disposed ahead of the traveling carriage 3, the selector 13 advances to a position corresponding to the knitting operation (A position). When the attraction is released in the release position disposed behind the traveling carriage 3, the selector 13 advances to a position corresponding to the tucking operation (H position). When the attraction is not released in either position, a position corresponding to the welting operation (B position) is maintained.
The selecting jack 12 is pushed by the tip 13d of the selector 13 and thereby advances within the needle groove 5. The butt 12a of the selecting jack 12 at each position is pressed by a B presser 16 and an H presser 17 provided on the carriage 3. By pushing down the butt 12a and sinking the selecting jack 12 into the needle groove 5, the needle jack 9 is also pushed down into the needle groove 5 whereby the butt 9a is separated from the knitting cam 10. The B presser 16 is provided to correspond to the welting position (B position) as a non-operative position of the knitting operation, and separate the butt 9a from the knitting cam 10 for almost the entire stroke. The H presser 17 is provided to correspond to the tucking position (H position). In this position, the knitting cam 10 acts on the butt 9a until the needle main body 8 advances part of the way toward the needle bed gap 7, and subsequently the H presser 17 pushes down the butt 12a to separate the butt 9a from the knitting cam 10. In the knitting position (A position), no presser is provided and the knitting cam 10 acts on the knitting needle 6 for the entire stroke.
Wires 18 and 19 penetrate the needle groove 5 in the longitudinal direction of the needle bed 2 to restrict the range of sliding displacement of the selecting jack 12 in the needle groove 5. Concaves 12b, 12c and 12d disposed inside a forked portion into which the rear wire 19 is inserted engage with the wire 19 to maintain the respective positions of the selecting jack 12. A guide cam which acts on the butt 12a is provided on the selector cam 14 so that the selecting jack 12 can retract to an initial position as the welting position after the knitting operation by the knitting cam 10 is completed.
JP-A 6-220752 discloses three-position locking type needle selecting apparatus capable of selecting the above-described three positions of A, H and B for needles and locking these positions such that a pushed-down condition of a butt on a selecting jack can be maintained even when the selecting jack is pushed up by a selector to advance to A position and the pressing by a selecting jack presser provided on a carriage is released. JP-A 6-200454 discloses two-position locking type needle selecting apparatus in which B position is shared by the non-operating welting position and the tucking position, and knitting needles are locked in B position in which a needle selection actuator operates at earlier timing. By locking in the welting position, a butt of a needle jack does not engage with a knitting cam while a carriage is traveling. As a result, occurrence of frictional damage and other damage of the butt and the knitting cam is reduced and sliding resistance caused by the shift of the carriage is decreased, thereby reducing the power cost.
In the weft knitting machine in which the knitting needles 6 perform knitting operations using the knitting cam 10 of the carriage 3 as illustrated in FIG. 13, advantages such as prevention of frictional damages and the like and the power cost reduction are expected to be offered by providing the above-described locking mechanism. Furthermore, in addition to the basic knitting operation, another advantage is expected to be offered in a process where a stitch loop is tightened in cooperation with sinker apparatus prior to knitting a new stitch, as disclosed in International Patent Publication WO01/36730. In this step, a stitch holding hook provided at the tip of the sinker is raised from a stitch pressing position to temporarily release the stitch from the stitch holding hook prior to formation of a new stitch. In this condition, the knitting needle is retracted from a needle bed gap to tighten the stitch by a stitch cam on the preceding side which is provided in a descending position where the knitting needle is retracted from the needle bed gap. Subsequently, the tip of the sinker is again lowered, thereby allowing the stitch to be caught by the stitch holding hook. Through this process prior to the stitch formation, the stitch already formed can be securely pressed by the sinker and the succeeding stitch loop can be successfully formed.
In this “preceding retraction” function, the “preceding retraction” is performed by the stitch cam on the preceding side of the knitting system with respect to the traveling carriage 3. At this stage, the butt 12a of the selecting jack 12 for the knitting needle 6 for which the non-operative welting position is selected as to the preceding stitch loop is released from the pressing by the B presser 16. As a result, the butt 9a of the needle jack 9 rises from the needle groove 5 and is then lowered by the action of the stitch cam on the preceding side. It is not preferable, however, that the knitting needle 6 which did not form a stitch is retracted at the time of the “preceding retraction” as described. A knitting yarn is drawn through the knitting needle every time the knitting system of the carriage 3 passes on the knitting needle 6 in B position where no operation is to be performed, which may give undesirable effects in terms of knitting operation such as wearing and cutting of yarn.
For solving the problem arising from the “preceding retraction”, locking the condition where the selecting jack is sunk in the welting position is also effective. However, in the locking mechanisms disclosed in JP-A 6-200454 and JP-A 6-220752, the advancing and retracting action of the selector is essential and thus pressers and other components are required for controlling this action. As a result, a large distance between the knitting systems is needed to provide a plurality of knitting systems on the carriage, which makes the carriage large-sized.
Alternatively, the unnecessary descending action of the knitting needles can be avoided by extending the width of the B presser which pushes down the butt of the selecting jack in the welting position to the position where the stitch loop is tightened or other actions are performed for the step where the stitch loop is tightened or other actions are performed. However, since the selecting jack is returned to B position as the initial position prior to the stitch loop formation at each knitting system, the butt of the selecting jack corresponding to the knitting needle for which the position selected is changed from B position to H position is also pressed by the B presser until the knitting needle advances to H position at the start of knitting operation by the succeeding knitting system when the carriage has a plurality of the knitting systems. As a result, when the knitting needle being pressed in this manner reaches the stitch cam used for the preceding retraction, the preceding retraction cannot be carried out. Accordingly, the length of the carriage in the traveling direction required by the cam increases and thus a distance between the neighboring knitting systems is enlarged, which makes the carriage large in size.